The present invention concerns an apparatus and method for heating a heat-shrinkable sleeve on a pipe. More particularly, but not exclusively, this invention concerns a method of applying a heat-shrinkable sleeve to a portion of a pipe and a heat-delivery apparatus for heating a heat-shrinkable sleeve around a portion of a pipe.
Pipelines for transportation of hydrocarbons, such as gas or oil pipelines, typically comprise sections of pipe welded together. Each section of pipe may include one or more outer coatings including for example one or more of a corrosion resistant coating, a plastic coating, and a concrete coating. To allow the ends of two sections of pipe to be welded together, the pipe coating at each end includes a cut-back, exposing the metal pipe ends to be welded together. The exposed pipe-ends once welded together may be protected by means of arranging a heat-shrinkable sleeve over them and then attaching the sleeve to the exposed pipe ends in the welded region by heat-shrinking the sleeve onto the pipe. The sleeve may be heat shrunk onto the pipe whilst the pipe is vertical (for example in a J-lay configuration) and/or generally horizontal (for example in an S-lay configuration).
WO 2010/130345 (Saipem SpA) discloses an apparatus for applying a heat-shrinkable sleeve to a portion of a pipe, the apparatus being in the form of a heater clamp that when closed has an inner surface of heater devices facing the pipe, the heater devices being arranged to define a generally cylindrical surface. In use, the heater devices may be operated to provide progressive and controlled heating of the sleeve. For example heating may start at a position that is in the middle of the sleeve in the axial direction and then subsequently proceed to heating at the axial ends of the sleeve. The embodiments illustrated and described in WO 2010/130345 concern a method of laying pipeline in S-lay mode.
The heating of the sleeve, which parts are heated when, and/or the relative orientation of the pipe causes movement of air in the gap between the pipe and the surfaces of the heater devices. For example, if a circumferentially extending heater apparatus were used to heat-shrink a sleeve onto a pipe in the J-lay configuration, hot air may rise up vertically through the gap between the heaters and the generally vertical pipe causing cooler air to be drawn into the gap at the lower end of the clamp apparatus. In the S-lay configuration, hot air may rise up vertically through the gap between the heaters and the generally horizontal pipe causing airflow currents in a direction circumferentially around the pipe, drawing cooler air into the gap at one or both ends of the clamp at the lowermost regions. In the S-lay configuration there may be a slight inclination in the pipe in which case, air may flow along the pipe in the general direction of inclination (from low to high). Heating in localised regions in the gap may generate convection driven airflows. Eddy currents may also be generated. It has been recognised by the inventors of the present invention that such airflows could be detrimental to the efficient heating of the heat-shrinkable sleeve and/or to how well the sleeve is secured/fixed to the pipe once the sleeve is shrunk onto the pipe.
The present invention seeks to mitigate the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide an improved method of applying a heat-shrinkable sleeve to a portion of a pipe and/or an improved heat-delivery apparatus for heating a heat-shrinkable sleeve around a portion of a pipe.